Conventionally, in the field of element sealing for electronic components such as transistors and ICs, resin sealing is commonly used for reasons of productivity and cost and the like, and epoxy resin molding materials are widely used. The reason for this widespread use is that epoxy resins are able to offer a favorable balance across many characteristics, including the electrical properties, moisture resistance, heat resistance, mechanical properties, and adhesion to inserts.
In recent years, as the packaging of electronic components on printed wiring boards has increased in density, the most common configuration for these electronic components is changing from conventional pin insertion-type packages to surface mounted packages. In order to increase the packaging density and lower the mounting height, surface mounted ICs and LSIs and the like have become thinner and smaller, the occupied volume of the elements relative to the package has increased, and the thickness of the package has become extremely small.
In order to cope with a shift towards even smaller and lighter packages, the package configuration is also changing from packages known as QFP (Quad Flat Package) and SOP (Small Outline Package) to area-mounted packages such as BGA (Ball Grid Array) that include CSP (Chip Size Package) which are more readily able to cope with increased numbers of pins, and enable even higher density packaging. Recently, in order to realize increased speed and multi-functionality, packages with new structures are being developed, including face down packages, stacked packages, flip-chip packages, and wafer level packages. Many of these packages have a single side sealing-type package structure, wherein only the surface on the side to which the elements are mounted is sealed with a sealing material such as an epoxy resin molding material, and solder balls are then formed on the rear surface to join the package to a circuit board.
As these types of packages are reduced in size and the number of pins is increased, the pitch distances between inner leads, pads, and wires and the like are narrowing at a rapid rate. As a result, the fact that carbon black, which has conventionally been used as a colorant, has an inherent conductivity has led to a problem in that aggregates of carbon black can become lodged between inner leads, pads, and wires, causing electrical defects.
Accordingly, methods in which organic dyes, organic pigments, and inorganic pigments are used instead of carbon black have been investigated (see Japanese Patent Laid-Open No. Sho 60-119760, Japanese Patent Laid-Open No. Sho 63-179921, Japanese Patent Laid-Open No. Hei 11-60904, and Japanese Patent Laid-Open No. 2003-160713).
However, these methods suffer various problems, including a deterioration in the coloring properties, a deterioration in curability, and increased costs, and have been unable to achieve a satisfactory level of performance.